HOW HAVE MULTIPLE INVASIONS ALTERED FOOD WEB INTERACTIONS AND STRUCTURE IN A EUTROPHIC LAKE OVER ALMOST 25 YEARS?

Invasive species have well-documented impacts on food web structure and water quality. However, predicting the interactive effects of multiple invasive species and their long-term impact on food web structure is challenging. Lake Mendota, WI experienced two successive invasions over the past 25 years: spiny water flea (Bythotrephes longimanus) was detected in 2009, followed by zebra mussels (Dreissena polymorpha) in 2015. Short-term investigations following each invasion revealed significant impacts on water quality and ecological interactions in the lower food web. Understanding how aquatic ecosystems respond to multiple interacting drivers through time is critically important yet remains difficult to quantify, especially for lower food web interactions involving bacterioplankton (microbes), phytoplankton, and zooplankton. Leveraging a nearly 25-year record of zooplankton and phytoplankton dynamics, along with a 19-year record of microbial data, we synthesize changes in species phenology and food web structure within and across each invasion regime. We highlight how zebra mussels and spiny water flea altered diatom community phenology in addition to driver-response relationships between nutrient load and several water quality metrics. We also show how successive invasions altered early season phytoplankton community structure and zooplankton-phytoplankton-microbial community trajectories. Understanding these complex interactions is crucial for effective conservation and management strategies in the face of growing invasive species threats.   

Primary Presenter: Tyler Butts, University of Wisconsin-Madison (tyler.james.butts@gmail.com)

Authors:

Tyler Butts, University of Wisconsin-Madison  (tyler.james.butts@gmail.com)

Katherine McMahon, University of Wisconsin-Madison  (trina.mcmahon@wisc.edu)

M. Jake Vander Zanden, University of Wisconsin-Madison  (mjvanderzand@wisc.edu)